The impact of low-frequency noise on human mental performance.

OBJECTIVES There is a growing body of data showing that low frequency noise (LFN), defined as broadband noise with dominant content of low frequencies (10-250 Hz) differs in its nature from other environmental noises at comparable levels. The aim of the study was to investigate whether exposure to LFN at levels normally occurring in the industrial control rooms can influence human mental performance (e.g., visual functions, concentration, continuous and selective attention) and subjective well-being. MATERIALS AND METHODS The study included 96 female and male volunteers, aged 19-27 years, categorized in terms of sensitivity to LFN. They worked with four standardized psychological tests (Signal Detection, Stroop Color-Word, Comparing of Names, and Continuous Attention) during exposure to LFN or broadband noise without dominant low frequency content (reference noise) at a level of 50 dB(A). Each subject was studied only once at randomly-assigned exposure conditions. RESULTS In the Comparing of Names Test, the subjects, regardless of the LFN sensitivity, showed tendency to make more errors during exposure to LFN than in the reference noise, and in the Signal Detection Test, they generally reacted faster (had shorter median detection time). In those noise conditions, however, the high-sensitive to LFN subjects, showed tendency to work less precisely (achieved lower number of correct responses in the Signal Detection Test) compared with the low-sensitive ones, while in the reference noise there was no difference related to noise sensitivity. The subjects categorized as high-sensitive to LFN also showed poorer performance than others during exposure to LFN in the Stroop Color-Word Test (a significant interaction between noise and noise sensitivity in case of reading interference index) and in the Continuous Attention Test (a tendency to more erroneous reactions). CONCLUSIONS These findings suggest that LFN at moderate levels might adversely affect visual functions, concentration, continuous and selective attention, especially in the high-sensitive to LFN subjects.